


Tit for tat

by tragakes (lejf)



Category: Transformers - All Media Types
Genre: Boob fic, Boobjob, Bottom Megatron, Drabble Collection, Dubious Content (not rlly), Exhibitionism, M/M, Megatron with a little valve, Plot What Plot/Porn Without Plot, sorry god, train-sex
Language: English
Status: In-Progress
Published: 2018-06-10
Updated: 2018-12-29
Packaged: 2019-05-20 10:28:17
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 3
Words: 4,344
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/14892903
Author URL: https://archiveofourown.org/users/lejf/pseuds/tragakes
Summary: Just Megatron with big boobs, small valve, and a surprised-but-mostly-delighted Optimus Prime.





	1. Chapter 1

**Author's Note:**

> Adi:  
> they start off fighting and op grabs a fist full of boob
> 
> tragakes:  
> :0  
> ok.  
> you've sold me.
> 
> adi's relevant [art](https://tfadi.tumblr.com/post/174520837059/welcome-to-another-session-of-self-indulgent)

Fighting against some mechs was cathartic, and fighting against others— _invigorating_. 

Optimus’ swing went just two nano-microns wide and Megatron pressed the opening: he shoved his servo into the plating on the underside of Optimus’ arm, transformed his claws directly into the seams there, and then took the hit as trade. The force of the punch was enough to send him reeling, but his grip into Optimus’ wires sent the Prime went tumbling right after and their claws slid against each other’s metal in agonising screeches. Optimus sliced up a knee in a move that would split open the armour of lesser mechs and Megatron met it with the heavy-duty plating of his arm, and then his unrelenting claws tore out some wires of Optimus’ arm, cords flying loose and sparks leaping between them. 

The injury didn’t seem to falter Optimus; his next blow knocked all the air out of Megatron’s intakes, aimed directly at the side of his chest-plates, intending to dislodge the armour there to somehow get to his spark. Megatron could’ve laughed. Let the Prime try! No mech would get through his chest-plate armour.

And the rest of it was a brazen mess of a fight, the two of them practically on top of each other, pedes trying to gut each other with each kick, rolling over again and again, claws trying to dig for any vulnerable seams to tackle advantages, and Optimus was leaking energon from his _neck_ when Megatron realised that his chest-plate had, in fact, been dislodged. Not broken — even Optimus would never managed that, but jutting out of place, and Optimus took that as an advantage and curled his servos beneath the metal there even as Megatron went straight for his neck again, digging his claws in there and twisting — but Optimus didn’t relent to protect his wires there, throwing his all into wrenching aside Megatron’s chest-plate.

It creaked unpleasantly just as Megatron’s claws pierced one of the outer lines and energon spurted between them — and then Optimus’ servos brushed _beneath_ what was under his chest-plates and Megatron’s entire body bucked, half through sheer surprise and heat and mostly instinctive reaction that re-positioned his claws and _shoved_ Optimus back until the other bot went skidding. 

Optimus raised a servo to his neck, a temporary patch slapped where his line was leaking energon, and Megatron noted with dismay that his plating was _jammed_ out of place, and he’d not do something as undignified as fight his own chest-plates to force it back where it should've been. 

His chest was exposed for the first time in more breems than he’d bothered to count, and Optimus’ optics were drawn towards that was swelled and round there, trembling from the touch of the cool air. Megatron had half a processor to retreat, but there was nothing undignified about his breasts — old designs for war-frame types that allowed for greater energon carrying capacity, could nurse sparklings or the injured, and also served a secondary purpose of refining lower-grade. There were few still with the design now, but it was nothing to be ashamed of! Megatron met Optimus’ gaze with a steely look. It was a matter of his heritage and origin. If Optimus thought he was going to retreat, he was sorely mistaken. 

They seemed to move in synchrony, Optimus weaving right beneath Megatron’s blow and reaching out his own servo to-

—gently cup those full and soft breasts, and Megatron gave a sharp intake and his punch glanced cleanly off Optimus’ plating, only for Optimus’ leg to hook around his and tug him forwards, off-balance. Megatron planted a claw against Optimus’ face-plates, intending to rip that face-mask straight off and punch through his processor if he wanted to bring this _close_ , but then one of Optimus’ servos moved, stroking his sensitive energon-sacs, a thumb flicking over one of the nozzles, and Megatron’s leg simply buckled. They crashed together to the floor, and in a sharp movement Optimus had them flipped. 

Megatron bucked underneath Optimus’ grasp, though possibly not as forcefully as he should’ve, his ventilations coming heavy and fast. Optimus slammed down as unshakeable weight on his back and kept his arms struggling to push him off and upright. 

“What are you _doing_?!” Megatron demanded, but words choked off as Optimus’ servos reached forward again, brushing over his breasts that practically quivered against the attention, and to his mortification, they were starting to leak energon from their nozzles already. They hadn’t been touched in– vorns, perhaps, and Megatron had overlooked their sensitivity. 

“I never knew you had these,” Optimus rumbled in his audials, and flicked over both the nubs again. Megatron bucked back at the sensation, and when his array met Optimus’ with a clang, he couldn’t contain the hot flush that bloomed inside him. His panel pinged a request to open and he denied it with full fury. 

“Of course it’s not _advertised_ ,” Megatron said. 

Optimus wrapped as much of each servo around his breasts, his palms broad and warm and lighting up every sensor in Megatron’s body as the nozzles were enveloped in heat. Megatron’s breasts were hefty, supple and fertile, practically cushioning beneath the pressure. Those fingers sunk into Megatron’s impossible softness and _squeezed_. 

Megatron’s panel flew open and his back arched, trying to fit more of his chest into Optimus’ groping hands. He heard Optimus huffing a laugh into his audials and the shift of plating and the pressure on his back lessened, Optimus readjusting to nudge his legs between Megatron’s and then spread them.

Megatron could’ve turned around and shot his blaster into Optimus’ helm and sent him straight into offline as soon as Optimus moved, but he didn’t. Instead, his valve clenched against the feeling of the open air and pooled with lubricant. 

Optimus gave one more indulgent knead and then pulled back. His servos wet were with energon, and he leaned back to look closely at Megatron’s valve- and paused. 

“You’re small,” he said, and Megatron’s engines instantly roared against the words. He heaved to get upright, his generous breasts swaying with the movement, but then Optimus’ servo planted itself in the centre of his back and the Prime blabbered, “No, no — it’s a good thing.”

Megatron reluctantly lowered himself back down, back onto his elbows, trying to ignore both his momentary lapse and the fact that he’d was still allowing Optimus to touch him. And what a ridiculous position to be in, his aft completely exposed to Optimus’ roving eyes, and even more ridiculous that his valve was laced with tiny tremors, sensitive and anxious to be filled. At the first brush of Optimus’ fingers, his back arched further, tipping his valve upwards, and that blue-painted finger sunk in slowly. Megatron gritted his dentae together to stop a moan from escaping. 

It was only one finger, and Megatron _swore_ he could take more. It wasn’t as though he made it a regular pastime to see how much his tight valve could admit — but for some reason Optimus saw fit to leave it as just one finger, rocking in and out of his valve. And _somehow_ he still felt that one finger keenly every time one of Optimus’ joints brushed over his nodes, his entire valve pulsing with the movement, his body shifting back to urge it deeper. 

His breasts shook slightly with the movement and then Optimus was leaning over him again, one hand down by his valve, the other reaching around to his breasts, kneading and tugging more persistently at them now, resting their silken weights in his hands. His fingers were tracing around the fluttering lips of his valve, flirting with the promise of adding another finger — and Megatron was caught in indecision between bucking forward or backwards. 

He settled for holding himself very still, as though any sudden movement would betray the fact that this was _happening_ , and that Megatron had at some point gone from fighting his nemesis to allowing his nemesis to fondle him gratuitously, to stroke his fingers over Megatron’s pliant nubs, to dip a second finger into his valve…

He tightened around the intrusion, a fresh gush of lubricant spilling around Optimus’ fingers. His intake fell open in a gasp; Optimus’ fingers were ruthless inside him, twisting and thrusting deep, only _two_ , and at the same time he fitted one of Megatron’s nozzles between clever fingers and pinched. 

“Prime…” he groaned, and couldn’t have said whether it was a plea or a reprimand or both. 

Optimus certainly took it as the former, because he said, “Trust me, I would love nothing more than to take what’s being offered,“— he corkscrewed his two fingers again, and Megatron’s optics half-shuttered involuntarily against it as Optimus’ voice dipped into the dark —“but this little valve isn’t going to let me in so easily.”

Megatron just jutted his aft out impudently, its curve tempting, and he felt something hot and bluntly heavy brush against the lips of his valve. He looked back, and Optimus put a hand on his aft urging it back down, patting the outside of his legs to urge them to press together until his valve was nestled wetly between his thighs.

The unforgiving pressure returned — that was Optimus’ spike, _Optimus’_ spike — sliding along the softer plating of his thighs, bumping just its tip against his valve. Megatron let his helm fall to the ground, and between the gap of his breasts where his nozzles were still standing to attention and a thumb was brushing over the edges of one and sending occasional shocks through his body, he could see the head of Optimus’ spike each time it rocked between the plating of his legs and brushed his valve. 

Its movement was strangely hypnotic, the head of it shining with lubricant both from Optimus’ spike and gathered from Megatron’s valve. Suddenly Optimus’ weight returned on his back and two servos were gripping his chest, pulling him back, up until he was flush with Optimus’ chest and he could feel Optimus’ nose nuzzling into his neck, mouthing over the wires there, his hands groping and teasing at Megatron’s breasts that now felt even more exposed than before. He was held out on wanton display like this, his legs squeezing Optimus’ obscenely large spike, his little valve’s lips parting and dragging over its surface each time it rocked forward, his chest dripping energon over Optimus’ fingers.

When he looked down, his nozzles seemed very small and delicate where they were bracketed between the thick fingers of Optimus. Optimus massaged, and out wept more drips of energon. 

Optimus’ engines and cooling fans were loud behind him, rattling his entire frame as he rocked his hips forwards in a facsimile of fucking. With each stroke forwards, Megatron felt his valve part around the head as it pushed through, the vulnerable insides of it revealed to Optimus’ spike. The nodes there crackled with charge and heady pleasure, and then Optimus withdrew and pushed forward again. Each time the tip pressed a little deeper, squirting in more pre-transfluid into Megatron’s small opening. Megatron writhed on it, trying to urge it deeper, but Optimus pulled back before he could.

He was opened up slowly, inch by inch, his breasts laved with the attention of Optimus’ servos until his tight hole was wet and stretched enough to admit maybe half the length of Optimus’ spike — and then Optimus began to fuck him. Kneeling in the dirt, he felt his aft rock each time Optimus thrust, his spike battering its way into his valve that was now supple and soft and welcoming. Shallow thrusts became deeper, pushing apart tight rings in Megatron’s valve, forcing groans from him as it plunged further and further and fucked in steady strokes. 

Megatron’s valve clung to it with each withdrawal, its lips wrapped obscenely tightly around what wasn’t even the full length of Optimus’ spike, and the next time Optimus thrust, it battered all the way to his gestation chamber. The round tip of Optimus’ cock was held there for a moment, experiencing Megatron’s valve ripple around him and the tiny slit flutter, before it was drawn all the way out and plunged back in again. It shoved at his gestation chamber as though demanding him to open it, and all Megatron could do was writhe, valve pulsing helplessly. 

Something that he wouldn’t admit was a whimper escaped him as he felt his little, exposed valve pressed wider by the thickening girth of Optimus’ cock. The pleasure of it was all-encompassing. Megatron’s whole frame bounced in Optimus’ hold and he clawed at Optimus’ servos, clutching his own breasts breathlessly as sensation overwhelmed him. His spike slapped against his torso plating, dribbling transfluid, though Optimus didn’t let up for a moment, pushing him closer and closer to overload. 

Megatron felt open even though he was filled, every inch of his valve scraped by Optimus’ spike inside him. It spread him wide and made him splash lubricant down between their thighs each time Optimus withdrew. Every part of him felt sensitive, gasping and groaning whenever Optimus flicked at a nozzle or thrust in deep. His spike rammed in over and over, pounding Megatron’s supple yet small valve, and finally the shy slit that was the opening to his gestation chamber gave, and Optimus’ spike pushed just the barest bit _in_. 

The sensation of Optimus filling him so fully was too much. Overload hit him hard, his whole body arching back, squeezing lewdly around Optimus’ cock and his breasts bouncing in Optimus’ hands, squirting from his spike as Optimus followed him into overload, transfluid spraying into his chamber as liquid so hot that Megatron could _feel_ it filling inside him. 

Optimus held him there, still with his spike pressed tight into him, breeding him with spray after spray. Megatron could feel his systems blinking and re-setting frantically. His entire body seemed to tremble with it, occasional twitches shooting through his thighs and his valve whenever Optimus’ spike twitched deep inside him. 

Optimus withdrew, and Megatron was prepared to slump and fall straight into recharge, except another thrust caught him off-guard and felt like it reamed his entire valve open. Optimus’ spike was so forceful and unstoppable, pounding into him until all he could do was clutch on and moan as Optimus fucked him harder and harder, trying to ram the whole length of his spike in. It pushed into his gestation chamber to shoot more transfluid into him — and Megatron held on in a silent cry, breasts heaving, Optimus nuzzling into his neck.

He was fucked through overload after overload until his spike would give only dribbles and his valve spasmed with every small movement, the Decepticon warlord brought to his knees by nothing but a pair of servos rolling his nozzles through their fingers and a spike that plowed him open. It should’ve been shameful, but the only shame he felt made his charge hitch up higher until it was swept away by the solidness of Optimus behind him, fucking him, splitting his tiny hole open, entering him again and again and whispering promises that he was beautiful — absurd — and that he felt so good and so tight.

And that Optimus wanted to see him heavy and lactating with their sparkling. But that was a thought best left for later.


	2. Chapter 2

Megatron looked gorgeous on his knees, though he wasn’t as defiant as Optimus might’ve fantasised in the past. Instead, there was a grudging air around him as he unlatched his chest-plate and let his breasts free.

He thought Optimus’ infatuation with his breasts was a little ridiculous, and always conducted himself as though just reluctantly humouring Optimus. But Optimus knew better. Megatron _loved_ it. He loved having his tits played with — he just wouldn’t admit it. 

Optimus’ spike rose, pressuring between those two mounds that Megatron squeezed together to create a tight, warm channel for Optimus to fuck into. 

The first time Optimus had tried to make Megatron move his breasts on his own, sliding them up and down Optimus’ shaft while Optimus sat back, after only several kliks of the building charge, Megatron had stopped and stubbornly refused to ‘do all the work’. 

‘You can’t bring me to overload?’ Optimus had asked, and— transparent as ever, and just as determined to prove him wrong — Megatron insulted him and then set to working his spike with renewed vigour until Optimus had sprayed transfluid all over his rounded breasts. 

Now, Megatron was cupping those breasts in his hands again, pressing them together, enveloping Optimus’ spike. It was almost better than plowing Megatron’s valve. This way, Optimus could see the way Megatron’s optic-ridges scrunched a little with the effort, the way he set his jaw, and could _see_ his spike sliding into and out of Megatron’s softness. The spike’s head bumped into view with each stroke of Megatron’s breasts, transfluid already gathering at the head. 

It was always a wet affair; from between Megatron’s fingers, his nozzles started to leak. Pink refined energon teased out from the nubs there, and Optimus reached out a thumb to swipe across them, then licked his thumb. The energon was thick and tangy, pure, and Optimus pressed his thumb towards Megatron’s tightly-set lips. 

Megatron gave him a look that seemed to say _really_? But opened his mouth to admit Optimus either way, shuttering his optics and sucking until his cheeks hollowed. Seeing Megatron _enjoying_ himself made heat flare in Optimus’ abdomen, his spike jerking in their snug place between Megatron’s breasts. A small spurt of transfluid painted across the top of Megatron’s tits and made them glisten. 

When Optimus removed the digit, the look Megatron gave him was positively wicked. Optimus actually groaned, tipping his helm until it bumped the wall behind him. But he couldn’t keep his optics away for long. He was drawn back to the rhythmic sight of his spike sliding between that softness, those full and lush breasts, so fertile and ready for sparklings, leaking energon all over Optimus’ spike, making it wet and easy to slide through. 

And soon Megatron won that challenge between them. Optimus began bucking his hips while Megatron held his breasts steady. Every time Optimus’ hips connected with the underside of them, they bounced with the movement, the swollen nubs tipping up slightly as Optimus’ spike slid far enough to bump the underside of Megatron’s chin. Megatron tipped his helm down, parting his lips, and there was something about the pose— Megatron with his head dipped, optics focused down on the sight of Optimus’ rutting spike, the tip pressing briefly between those lips as Megatron teased out his tongue to catch a taste before Optimus drew back to rut up again— that was so contained and _demure_ that it sent Optimus instantly careening over the edge.

Optimus tried to convey his adoration for that pose in one word, in one choked ‘Megatron!’ before he rutted up farther than before, Megatron’s faceplates briefly flashing surprise as Optimus’ spike pushed between his lips and stayed there, gushing transfluid. Megatron lapped it up, tonguelaving broad streaks over Optimus’ tip as he suckled, and began squeezing his breasts rhythmically, dragging them up and down the sides of Optimus’ spike. 

Oh, Megatron was just too much to be true. His Autobots would _kill_ him if they found out, but there was no way Optimus could stop. The sight of Megatron obediently there, his mouth sealed around Optimus’ spike, his breasts leaking for Optimus—

He pushed Megatron down and Megatron let him, Optimus following. He’d frag Megatron until morning. 

 


	3. Chapter 3

**Notes for the Chapter:**

> Hey long time no see, sorry i’m been in college but here have some short pwp lol
> 
> This one’s completely on its own. no premise. just enjoy the smut. hahaha i’m a degenerate

 

Megatron hadn’t taken the subway before, so it was natural that he he regarded the train with suspicion. What if the magnetism failed? What if the train left the tracks? Hadn’t there been an incident last vorn where one had derailed and killed hundreds of bots on board? They were hurtling at a few hundred kilometres per decaklik. No matter how armoured he was, he wouldn’t survive that sort of collision.

“Relax,” Optimus said, into his audial. Megatron’s grip on the handrails running along the ceiling of the train tightened. He swore that Optimus was finding some amusement in this. There was a certain teasing lilt to his tone that Megatron was all too familiar with. 

It didn’t help that there were so many bots on board. Megatron had tactfully positioned himself in the corner of the carriage where he had walls on two sides and he could narrow his optics at the Iacon train-goers. Optimus stood next to him, one arm snug around Megatron’s waist (his waist was the narrowest part of him, one of the only places where Optimus could actually wrap a full arm). That one arm even started to tap playfully at Megatron’s hip.

The carriage was stuffy, too-warm with the running engines of many bots. There was one smoking with some sort of substance from its vents and filling the place with a light mist. Megatron’s face morphed into a deeper scowl. Kaon did smell bad, but somehow this was worse. This wasn’t dirty-bad. This was hedonistic-bad. 

“Relax,” Optimus repeated, and before Megatron could gripe about _what’s relaxing about being stuffed into a tin can with all these Iacon idiots_ because Optimus shifted his hand down to palm at Megatron’s rear, pausing briefly at his port. 

“What do you think you’re doing?” Megatron’s voice had dipped into a low hiss, though the rabble of conversation was loud enough to mask even the smooth sound of the train splitting the wind. No one would hear what they were saying to each other.

“Relaxing you.”

“If this is about the challenge you made-“ Megatron bit off his words as Optimus pushed a finger inside him. He was still stretched and wet from some of their ministrations earlier. Tender, too, clenching tightly at the intrusion. Optimus toyed just at the entrance of his port and felt it spasm. 

“–When I said you’d enjoy the subway. Yeah.”

“You _fragger_ ,” Megatron said. Then, “ _Mmh-!_ ” He could feel the heat rising in his faceplates. Optimus really was out of his mind. Fingering Megatron in a public place like this was just outrageous! “You- you are _not_ going to- ahh-“

Optimus said nothing, but Megatron felt his smile against his shoulder as Optimus pressed against him and began pumping into him with vigour, his finger driving deep into his tight port, feeling the cling of his insides and then drawing out again. Megatron found himself rocking back almost subconsciously. It wasn’t that he was accepting this — it just felt too good! It was Optimus’ fault for making it feel so damn good! Especially when he added another finger alongside the first, rubbing against Megatron’s inner walls and scissoring inside. His fingers crooked this way and that, touching nodes that made Megatron tremble.

Megatron hardly noticed that Optimus had snuck his other hand around the front to his chest plate and had undone one of the side latches. It meant that his chest plate hung open, just slightly. The gap was small enough for Optimus to fit a hand and wrist through. From there he grabbed a handful of Megatron’s breast and squeezed. 

Torn between rocking back on Optimus’ fingers in him or the hand rolling a nozzle between his fingers, Megatron picked neither and instead let Optimus have his way. Optimus tugged the nub of his breast, simultaneously fucking his greedy hole with his fingers. The dual pleasures were already almost too much, his port squeezing and dripping lubricant down Optimus’ hand as he arched his back. But never did Megatron fully forget that they were in a public area and that in any moment someone might notice. 

It wasn’t just the threat of discovery, but the _brazenness_ of it. It made him burn even hotter knowing that Optimus would want to touch him so badly that he wouldn’t stop even on the subway. Megatron imagined briefly if Optimus would do it in other places. If, when they were just walking back to their home, Optimus pulled him aside and took him right there. If, when Megatron was in the corridor trying to get to his office, Optimus pushed him against the wall and shoved his spike straight into Megatron’s port. Here, Megatron had both arms raised and holding onto the handrail, not making any effort to bat Optimus away, just letting Optimus grope and fuck him.

They both froze as the train stopped and bots left and entered. Megatron’s back was to the wall so no-one would see his dripping port stretched around Optimus’ fingers, and even if anyone saw Optimus’ hand behind Megatron’s chest plate, they wouldn’t assume it was kneading his soft plush protoflesh, thumb brushing circles over his sensitive nubs…

Another finger breached past the small rim of Megatron’s hole. It was immediately squeezed and Megatron rocked back with a silent moan as the train started moving again. Optimus couldn’t help looking at the way Megatron’s ass spread around him. It was amazing how tight he was every time. Though the true thing that had Optimus’ spike twitching behind its sheath was the glazed look in Megatron’s optics, the way that his lips parted and he bit his glossa to keep from making noises. 

“You’re kind of a slut,” Optimus murmured. Megatron’s optic-lids shuttered like the rapid beat of a heart.

The train hit a turn hard; Optimus’ fingers slid into that perfect spot where a cluster of nodes ignited Megatron from the inside-out and his overload crashed into him. Among the commotion of bots scrambling to regain their hold, Megatron shook and trembled and came apart. He made a sound like a mewl caught in a gasp and Optimus felt wash gushes over both his hands. When he withdrew them they were coated with lubricant from Megatron’s valve and energon from Megatron’s nozzles.

Then he was met with Megatron’s thunderous expression. “You’re going to pay for this.”

Optimus pushed a finger back in, watching the way Megatron's scowl melted into something more wanton, blush rising.

"We've got six more stops to go."

 

**Author's Note:**

> for adi :D
> 
>  
> 
> & more to come


End file.
